Hydraulic motor operated clutch



March 2l, 1950 E. A. RocKwELL HYDRAULIC MOTOR OPERATED CLUTCH Filed Dec.24, 1943 'Sheets-Sheet l Ivor/1 /eve/.

March 2l, 1950 `E. 'A. RocKwELL 2,501,005

l HYDRAULIC MOTOR OPERATED CLUTCH Filed Deo. 24,- 1943 3 Sheets-Sheet 2Match 2l, 1950 E. A. RocKwELL v 2,501,005

HYDRAULIC MoToR CPERATED CLUTCH Filed Dec. 24, 1943 Sheets-Sheet 3 TaVac.

vernal/arf .Edward `Q .Foc/me!!! @gw/@7gg Patented Mar. 2l, 1950HYDRAULIC MQTOR OPERATED CLUTCH Edward A. Rockwell, cleveland, ohio,assigner, by mesnc assignments, to Borg-Wamer Corporation, Chicago, IIL,a corporation of Illinois Application December 24, 1943, Serial No.515,602 3 Claims. (Cl. 192-91)` This invention relates generally tohydraulic pressure-operated devices and particularly to hydraulicmotor-operated friction clutches.

The problem of effectively adjusting friction clutch assemblies for wearhas been a serious one for a long time and has remained unsolved priorto the present invention. This problem, in its specic aspect as regardsfriction clutches, arises particularly out of the fact that a smallamount of wear in the friction disc is multiplied many times in itseffect on the long lever arms normally engaged by the axially disposedoperating collar. The problem has been further aggravated by practicallimitations as to pedal travel and increasing demands for power as thesize and capacity of the clutch has been increased, thus rendering theavailable mechanical lever and linkage mechanisms between the operatorand the clutch ineffective to accomplish satisfactory clutch operation.,f

It is, therefore, a broad object of my invention to provide in anoperative mechanism, subject to wear in the connecting parts thereof, animproved automatic means functioning in the normal course of operationthereof to adjust for such Wear, without requiring any separate manualadjusting operation.

A more particular object of my invention is the provision of a frictionclutch assembly having an improved arrangement of hydraulic pressurefluid responsive operating means, including an arrangement forautomatically adjusting the same for wear, particularly wear in thefriction element of the clutch.

It is a further object to provide an operator controlled hydraulicpressure fluid supply link for the clutch operating motor and a powerpressure intensifier interposed in said link effective to amplify thepressure in a definite ratio to that applied by the operator andincluding means automatically operable with successive operations by theoperator effective to adjust the assembly for wear in the frictionelement of the clutch.

It is a more detailed object to provide in an Y arrangement of the abovecharacter for causing the wear to gradually move the displaceableelement of the motor further and further in the direction of the closedend of the cylinder when the clutch is in engaged position and providinga receiving and storing arrangement for the excess fluid due to suchreduction in volumetric capacity, the initial volumetric capacity of themotor being made sufficiently large to provide for the said reductiontherein as wear takes place.

Further and more detailed objects, advantages 2 and uses of my inventionwill become apparent from a reading of the following specification takenin connection with the accompanying drawing which forms a part thereofand wherein:

Fig. 1 shows schematically the relative arrangement of the importantparts of my invention as applied to the operation of a, clutch;

Fig. 2 is an enlarged, cross-sectional view of the clutch and hydraulicmotor for operating the same;

Fig. 3 is an enlarged, cross-sectional view of the power pressureintensifier unit for operating the clutch motor; and

Fig. 4 is a cross-sectional view of the master cylinder assembly.

Referring in greater detail to the flgures of the drawing, I havedisclosed a preferred embodiment of my invention in its specialapplication to clutch operation. In the broader aspects of my inventionit will be understood that the same has application to the operation ofother mechanism wherein similar therefor exist.

A friction disc type clutch assembly indicated generally at l0 isprovided with a special arrangement of hydraulic pressure fluidresponsive motive means indicated generally at Il for accomplishing therelease of the clutch, this motive means being supplied withI operatingpressure through a, power pressure intensifier unit I2 under the controlof a remotely located manually operable master cylinder assembly I3including a reservoir I 3a into which excess liquid is introduced incompensating for wear. These principal parts are arranged and theirsubordinate components are so correlated that wear in the clutch isautomatically compensated for and the necessary adjustments effected formaintaining zero clearance at all times between the elements in theoperating linkage from the manual operative all the way through to theclutch. This correlation is such that as the friction disc of the clutchlll is worn the same is effective through the operating levers forming apart thereof to gradually decrease the volumetric capacity of thehydraulic motor with the expansible element thereof in clutch disengagedposition and this decrease in volumetric capacity is automaticallycompensated for by having the piston in the master cylinder uncover aport which communicates with the fluid reservoir when this piston ismoved to retracted position with the result that any excess fluid isejected to the reservoir.

It will be noted that this mode of coaction is quite distinguishablefrom that present in the opproblems of wear and adjustment eration of"make-up arrangements now in common use wherein any loss of fluid due toleakage, for example, may be made up by having the master cylinderpiston uncover a port in communication with the make-up reservoir,allowing makeup fluid to flow from the reservoir into the fluid link asdistinguished from removal of fluid from the link into the reservoir.

It will thus appear that as wear takes place during the life of theassembly fluid replacement will be required less frequently if noteliminated altogether.

The well-known clutch arrangement l0, in which my invention isincorporated in a novel manner, may include a power input shaft 20,supporting in driving relation therewith a iiywheel or back plate 22 anda pressure plate 24 also drivingly supported in axially adjustablerelation to the back plate. A friction disc assembly 26 has the frictionfaclngs 28 thereon interposed between the back plate and the pressureplate, the hub portion 30 being supported on and drivingly connected tothe power output shaft 32 by the usual splined arrangement. Coilcompression springs 34 urge pressure plate 24 in the direction ofengagement with the friction disc 28 and the reverse or release movementof the pressure plate is accomplished through a plurality of radiallyinwardly extending pivoted levers 36. Only one spring 34 and one lever36 are shown for simplicity.

One of the most serious and troublesome problems in connection with thesatisfactory and eilicient operation of this class of clutches resultsfrom the wear in the friction facing of the clutch disc. Many proposedsolutions have been oiiered heretofore for providing the requisiteadjustment' necessary to compensate for this wear.

This invention is particularly directed to the provision of andarrangement for operating the levers 36 in a more effective andsatisfactory manner than herebefore provided which arrangement alsoincorporates a solution to the problem of adjustment for wear in theclutch parts including particularly wear in the friction facing. Thepresent arrangement is effective to maintain zero clearance in theentire operating linkage extending from the pressure plate to theoperating levers 36 through pressure fluid responsive operating motorIl, power intensifier l2 and manually operable master cylinder assemblyI3.

Pressure fluid responsive arrangement or motive means Il includes afirst tubular member 38 received in embracing relation about poweroutput shaft 32 with the inner terminal portion thereof adjacent the hubof the clutch disc assembly 26. The outer terminal portion of tubularmember 38 has a base or flange 40 extending radially therefromsupporting a second tubular member 42 of larger diameter than tubularmember 38, the base member 40 also functioning to close the spacebetween the adjacent terminal portions of tubular members 38 and 42 tothus define therebetween a cylinder 44. Tubular member 42 is shown asbeing fastened to flange 40 by a plurality of cap screws 46. It will beapparent that this construction of the tubular members is made tofacilitate manufacture and assembly and that the same may beaccomplished otherwise, such for example as making the two tubularmembers 3B and 42 in one integral assembly. A third, piston-like tubularassembly 48 includes a piston portion proper 50 operable in cylinder 44and an external portion 52 the inner periphery of which guldably engagesthe inner tubular member 38. The external terminal portion thereofcarries an anti-friction bearing and ring assembly includinganti-friction balls 54 and cooperating ring 56 engaging the innerterminal portions 36a of clutch operating levers 36. As these levers 36rotate with the pressure plate 24 the anti-friction rollers 54 and ring56 limit to a minimum the friction imposed upon piston assembly 48 whichis held against arcuate movement by a special arrangement to bedescribed.

It is important to note that in a clutch of the present class, asfacings 28 become worn the same will be evidenced by the gradualshifting of the off position of terminal lever portions 36a, this offposition of the levers being the position in which the pressure plate 24is in engagement with the friction facings known as the clutch engagedposition. Since the lever arm in the present type of clutch is muchlonger than the work arm, wear of the clutch facings is thus amplifiedin its effect on shifting the off position of the levers 36. It isimportant to note that while wear in the friction facings results ingradual increased movement of the pressure plate 24 to the left in thedrawing this wear is reflected through the terminals 36a of the leversby the reverse movement thereof to the right. Referring to cylinder 44,particular attention is directed to the fact that the above condition isfully taken care of by providing ample initial volumetric capacity,designated VN, within said cylinder, with a new clutch facing and withpiston 5U in clutch. engaging position. This initial volumetric capacityis sufficient to provide for the shifting of the inner terminal positionof piston 50 as full wear in the clutch assembly takes place duringwhich the volumetric capacity of cylinder 44 in clutch engaged positionis reduced to a value designated VW. For example, I have found fromactual construction and test that a clutch arrangement of the typedisclosed will give very satisfactory operation for the wear life of thefriction facing if the motor is given an initial volumetric capacity VN,with the pressure plate engaged, substantially two and one-half (2l/2)times the volumetric displacement of the piston in effecting completerelease4 of the clutch. Specifically, I provide about 21/2 cubic inchesinitial volumetric capacity where the piston displacement in releasingthe clutch is one cubic inch. This will, of course, vary with differentlever arrangements and lengths of lever arms and is readily obtainableby examining the position of lever terminals 36a with a new clutchfacing in position and comparing this with the position of theseterminals with a completely worn facing in position in the clutch, orthe same may be readily calculated. y

For the purpose of further insuring against the arcuate movement of thepiston assembly due to frictional contact with the lever terminals 36athere is provided a guide 58 which may be in the form of a pin mountedon radially extending base flange 40, this guide pin extending in agenerally axial direction in radially spaced relation to piston assembly48. Guide pin 58 may be threadably mounted in flange 40 and lockedthereto by nut 58a. A radial flange 68 extends from piston portion 52and has extending radially therefrom a guide shoe 62 which may befastened to the flange by screws 64, guide shoe functioning incooperation with guide pin 58 to prevent arcuate movement of the pistonassembly. While guide shoe 62 may be formed integral with radial flange60, it has been found more expedient from a manui'acturing point ofview, to construct the same in the manner described. A coil compressionspring 58h has one terminal thereof engaging lock nut 68a and the otherterminal engaging a follower guide shoe 50c effective to exertsufficient pressure of follower shoe 58e against guide shoe 62 forpreventing piston 50 from being shaken to the right in Figure 2 beyondits normal off position. This same result may be accomplished byproviding suflicient friction between guide shoe 62 and guide pin 58.

The cylinder assembly is preferably arranged to be fastened to thetransmission housing (not shown) as by means of bolts 40a passingthrough base flange 40. Output shaft 32 is freely rotatable within innertubular member 38, there being provided a threaded portion 38a on theinner peri-phery of tubular member 38 for the purpose of feeding backany lubricant that may tend to leak from the housing side along shaft 32in the direction of the clutch assembly.

For the purpose of sealing the moving parts oi the motive means againstthe entrance of foreign matter, a flexible boot 66 is provided, oneterminal of which is upturned to form a toe-like engageable rim 68receivable in an annular groove 60a of radial flange 60 and confinedtherein by means of a plurality of circumferentially spaced washers 64aconflned under the heads of screws 64. The opposite terminal of boot 66is slightly enlarged to form a flexible bead or ring I0 received in acomplementary peripheral recess 42a formed in the second or outertubular member 42. The space within the flexible boot 66 is vented tothe atmosphere by means of a passage 1| formed in the wall of outertubular member 42 and a similarly formed transverse lpassage 'I4containing the usual type of air vent iitting 16.

Entrapped air in cylinder 44 may be readily removed by means of airbleed assembly 12 of the usual construction which may include a tubularexternally threaded housing 12a mounted in the threaded terminal ofpassage 42h in the outer tubular member 42, this housing 12a beingclosed by a readily removable threaded closure plug 12b. Operatingpressure uid is introduced to and withdrawn from cylinder 44 throughport 44a in the wall of outer tubular member 42.

With the increased use of heavy automotive vehicles requiring largecapacity clutches, it is no longer practicable to rely completely onmanual y operation of these clutches. The need for applying power to theoperation of clutches as a supplement to the manual effort is wellestablished. However, I am not aware of any previous arrangement whichoperates in an equivalent manner to provide the cooperation and mode ofcoaction herein disclosed. The important requirement herein contemplatedis the provision of free uninterrupted uid communication through thepower intensifier or amplier unit in the oif position of the unit makingpracticable the novel compensating arrangement to be described.

While other forms of power pressure intensiers or amplifiers may beemployed so long as the same satisfy the required mode of coactionherein contemplated, AI prefer to use the form indicated generally atI2. The details of this power pressure intensifier unit, aside from thenovel combination thereof in the present arrangement, are being coveredand claimed in a copending application Ser. No. 507,227, illed October20, 1943, upon Intensifier for application of power.

Essentially, for the purpose of this case, a diaphragm or piston housing80 contains a vacuum responsive power applying diaphragm or pistonassembly 82 eective to operate a power pressure intensifying oramplifying piston 84 in response to the delivery of a predeterminedvalue of control pressure from master cylinder I3. Manual controlpressure when applied by application of the operators foot to pedal |3bpasses through conduit 86, open transition valve assembly 88, aboutmodulating valve assembly control piston in cylinder 92, throughtransverse passage 94 into power applying cylinder 96 out throughdelivery port 98 and conduit |00 to inlet port 44a of cylinder 44. Thiscondition of communication between the master cylinder I3 and the clutchcylinder 44 through the power pressure intensifier prevails for allvalues of pressure below said predetermined pressure thus providingmanual delivery of pressure to said clutch motor cylinder 44 up to saidselected value of pressure and providing for free unobstructed return ofpressure uid from the clutch cylinder 44 back through the power pressureintensiiler to the master cylinder when force of the operators foot isremoved from pedal |3b. This mode of operation through the intensifierunit I2 is significant in connection with automatic adjustment for wearin the clutch disc as will appear.

When the operator has applied a selected value of pressure to theoperation of master cylinder I3 the same will act upon power pressureintensifying piston 84 and move the same to the right in the drawingagainst the action of a control coil compression spring ||2, thuseifecting the operation of the modulating valve assembly |04 which inturn controls the introduction alternately of vacuum'and air to powerapplying diaphragm assembly 82. This power applying diaphragm assembly82 is normally submerged in vacuum on both sides thereof. This vacuummay be supplied from any available source such as a vacuum pump or themanifold of the engine (not shown).

Modulating valve assembly |04 comprises a disc-like vacuum control valve|04a reciprocable into and out 'of engagement with a coaxiallyreciprocable seat |042), the latter being mounted on a surroundingiiexible diaphragm |04c supported about one terminal of a passage |06 inthe power diaphragm hub portion 82a. The opposite terminal of passage|06 is formed to provide a second valve seat |06b having a second discvalve |04d cooperating therewith for modulating or controlling theintroduction of air. A light coil compression spring |04e applies aforce urging air valve |04d in the direction of its seat |031). Valveseat |04b cooperating with vacuum control valve |'04a has an externallythreaded tubular protuberance connecting the same with a correspondingprotuberance extending from air control valve |04d providing forreciprocation and preventing relative axial movement between valve seat|04b and Valve |04d. Valve I04d is formed with a passage |04ftherethrough for the communication of vacuum to the right side of powerdiaphragm assembly 82 when vacuum valve I04a is open to submerge bothsides in vacuum as will appear. Vacuuml control valve I04a is mounted ona coaxially extending valve stem |04g guidably mounted within thepassage |04f in air control valve |04d. Valve stem I 04g is connectedwith a walking beam-like lever 08 which has a xed pivotal support I08aintermediate the ends thereof on hub 82a. The opposite terminal portionof lever |08 engages with the inner terminal of modulating controlpiston 90. A balancing diaphragm assembly ||0 includes an auxiliarydiaphragm ||0a having the central portion thereof connected with walkingbeam lever |08 by a stem ||0b and the peripheral portion thereofconnected with the power applying diaphragm or piston hub 82a. A controlcoil compression spring ||2 is interposed between hub 82a and walkingbeam |08 in such a manner that modulating control piston 90 is effectivethrough walking beam |08 to compress control spring ||2 following theinitial movement'l of the power applying piston 84 to the right inresponse to manual pressure as will appear. Initially walking beam a|08is effective, as a result of the shift of power p'iston 84 to the right,to compress control spring H2 independently of modulating valve controlpiston 90 to crack open air valve |04d to effect the reversal ofmovement of power diaphragm assembly 82. Balancing diaphragm assembly||0 is given an effective area corresponding to that of vacuum controlvalve |04a to thus cancel out the effect .of the pressure differentialacting on vacuum valve |04a and which would otherwise be transmittedthrough walking beam |08 to control piston 90. The clearance between theconnecting stem 0b and the opening B2b in diaphragm hub 82a may berelied upon to communicate pressure to the under side of diaphragm I|0a. Stem' ||0b passes through an opening in walking beam lever |08 anda radial flange |0c controls the limit of movement of lever |08 awayfrom hub 02a. A stop sleeve ||0d limits the movement of lever |08 towardhub 82a. Inner terminal guide portion ||0e of stem |I0b guidablycontrols the relative movement between modulating control valve piston90 and the hub 82a.

Communication with the atmosphere is had through air inlet ||4, bore 84aof power intensifying piston 84, transverse passages 84h and |0811leading to air valve seat |061).

When as above stated, the manually delivered fluid pressure from mas'tercylinder |3 reaches a predetermined value determined by the strength ofcontrol spring ||2 power pressure intensifying piston 84 will be shiftedto the right in the drawing by the action of the pressure thereon,moving air control valve |04d to crack the same open sufficiently topermit the admission to chamber 80o of a relatively small amount ofatmosphere.

This admission of atmosphere to chamber 80e is effective to increase thedifferential pressure between opposite sides of said vacuum powerapplying diaphragm assembly 82 with the result that power diaphragmassembly 82 is stopped from further movement to the right and is shiftedin the reverse direction to the left in the drawing, carrying with itpower pressure intensifying piston 84` and acting through walking beam|08 to lap air valve |04d. The manually delivered pressure passing frommaster cylinder |3 through conduit 86 and transition control valveassembly 88 acting on modulating valve control plunger 90a of piston 90becomes effective to cause the same to move to the left in the drawingwith the result that transition valve 88a carried in the end of piston90 is moved away from stop 88o normally holding the valve open and valve88a caused to close under the influence of spring 88e, shutting oif uidcommunication between cylinder 82 and master cylinder I3 but notdisturbing the application of master cylinder pressure to modulatingvalve control piston 90 which pressure continues to act on the rear sideof transition valve assembly 88. The force which initially causesmovement of control piston 90 is of course the result of pressure fluidin chamber 82 and the value of the pressure required is determined bythe cross sectional area of the opening through which the plungerportion 90a is being expelled in the direction of control spring ||2 andby the resistance offered by control spring H2.

It is important to note that working surface 90b of modulating valvecontrol piston 90 is given a predetermined area having a definitefractional relationship with reference to the effective area of the backside or master cylinder side of the piston 90, with the result that themanual pressure delivered by the master cylinder I3 does a constantdefinite ratio of the total output work delivered to cylinder 44 of theclutch motor and what is equally important the operator receives adefinite reaction or feel of the pressure being applied to the clutchmotor. It will be noted that power pressure intensifying piston 84 is ineffect a hydraulic fulcrum that is shifted by power applying diaphragmassembly 82, the power applied to the diaphragm bearing a definite ratioto the power applied to the end of the hydraulic lever, namely, thatapplied to piston 90. Similarly the travels of valve control piston 90and amplifying piston 84 are correlated so that the two move together,it being impossible for the power amplifying piston to ever run ahead ofthe control piston 90.

When the operator desires to again effect engagement of the clutch theforce on pedal |3b is relaxed and spring |3c, together with the pressureiiuid, acts on piston i3d of the master cylinder returning the same tothe position shown uncovering port |3c leading to reservoir |3aeffecting compensation for the wear as will appear. Coil compressionsprings 34 of the clutch act through clutch levers 35 to move pistonassembly 48 of the clutch into cylinder 44, forcing pressure fluid backthrough line |00. The returning pressure acts on amplifying piston 84and on surface 90b of valve control piston 90 moving these pistons tothe right in the drawings and back to their off position. As transitionvalve 88a engages its limit stop 88h the same is opened to reestablishcommunication between the clutch motor cylinder 44 and the mastercylinder piston Special attention is now directed to the fact that asthe clutch facing has become worn the piston portion 50 will be requiredto move deeper into its cylinder 44 in order to effect completeengagement of the clutch. This is made possible by the fact that mastercylinder piston has uncovered port |3c and transition valve 88a beingopen there is unobstructedor unrestricted flow to reservoir |3c. Asufficient positive pressure is maintained at all times to keep out air,the reservoir |3c being disposed in an elevated position. Thus there isprovided an effective arrangement for automatically adjusting for anywear and for maintaining zero clearance in the operating linkage whileat the same time providing power operation. It will be noted furtherthat the usual valve mechanism in the master cylinder for maintaining apositive pressure has been eliminated as well as the pressure dropcaused thereby.

It will be noted that in passing over rough surfaces with the clutch inengaged position, any tendency to shake piston 50 further to the rightin Fig. 2 might tend to transfer uid back through conduit |00,intensifier l2, conduit 86 and port |3c into reservoir |3c but for thespecial provision of means to prevent this from happening.

As above pointed out, spring 50h performs this important function in thepreferred construction herein described by way of example.

In the further essential operation of the power unit |2 upon clutchengagement, return spring ||6 is so chosen as to move power diaphragmassembly 82 to the right causing walking beam or lever |08 to closevacuum valve |04a-opened by Ithe relaxation of force on pedal I3b-andsubsequently crack open air valve |04d admitting enough air to causepower diaphragm assembly 82 to shift to the left an amount sufficient tobalance spring ||6 and lap air vvalve |04d, this position being shown inthe drawing.

For the purpose of filling the system with liquid, including effectingthe desired initial level cf liquid in reservoir |3a as well as forbleeding air from the system, there is provided a reservoir oil bleedand level control assembly indicated generally at |30. This bleedassembly comprises essentially a depending tubular member |32 threadablymounted in the reservoir cover and extending downwardly to the correctlevel for positioning ball check valve |34 in a position where the samewill be effective to establish the proper initial liquid level with anew clutch plate in the `clutch assembly and providing for sufficientspace above the liquid level in the reservoir to receive additionalliquid ejected from the system during the wear life of the clutch plateafter compensating for such wear. Ball check valve |34 is urged in thedirection of its seat by a coil compression spring |36. The outerterminal of tubular member |32 may have threadably mounted therein ableed assembly of the same form as air bleed assembly 12 described abovein connection with clutch motor I and including a threaded closure plug|40.

It will now appear that the system may be charged with the requiredvolume of liquid and the air bleed therefrom while at the same timeleaving the requiste space in the reservoir above the initial liquidlevel by first removing closure plug |3e and connecting thereto theusual liquid supply unit. Air bleed closure plug 12b and oil bleedclosure plug |40 are then removed and with the clutch in off position,as shown in Fig. 2, liquid is introduced until air free liquid isdischarged from air bleed assembly 'l2 whereupon plug 12b is replaced.When the liquid level in the reservoir has risen to that indicated asthe initial level then further rise of liquid in the reservoir will beevidenced by liquid being discharged from oil bleed |38 whereuponfurther delivery is shut off and oil bleed closure plug 40 as well asreservoir closure plug |3e are replaced.

While I have disclosed my invention in connection with a certainspecific embodiment thereof, it is to be understood that this is by wayof example and not limitation` my invention being defined by theappended claims which should be given a scope commensurate with theprior art.

I claim:

l. In an arrangement for transmitting operating pressure to a device tobe moved through a predetermined range and automatically adjusting forwear therein, said arrangement including means defining a linkage havingan off position which is gradually changed due to said wear, meansdefining a hydraulic motor for operating said linkage, said motorincluding a fluid displaceable piston-like element for moving saidlinkage through said predetermined range and being so arranged that saidgradual change of position of said linkage due to wear is effective l0to reduce the volumetric capacity of said motor with said piston in itsretracted position, means defining a pressure intensifier for deliveringoperating pressure to said motor, a master cylinder including a manuallyoperable piston therein deliverng pressure to said intensifier forcontrolling said power intensifier, said piston being effective todeliver a definite proportional part of the total operating pressure tosaid motor, a fluid storage chamber, conduit means connecting saidmaster cylinder with said intensifier and said intensifier with saidmotor, means placing said storage chamber in fluid communication withsaid conduit in response to movement of said master piston to the offposition thereof whereby the decrease in volumetric capacity of.' saidmotor in the retracted position of said motor piston resulting from saidwear is effective to cause delivery of excess fluid to said storagechamber and thus automatically compensate for said wear and meansoperable on the movement of said linkage a predetermined distance in onedirection effective to control the extent of the further movement ofsaid motor piston in the retracted direction during periods betweensuccessive operations, whereby the volume displacement of the pistonwill remain substantially constant during successive operations. I

2. In a clutch and power operating arrangement therefor, including afriction disc of the type having spring means for effecting theengagement thereof and linkage means for effecting the release thereof,a hydraulic motor for operating said linkage, said motor including aiiuid displaceable piston-like element for moving said linkage through apredetermined range and being so arranged that wear of said clutch plateis effective through said linkage to reduce the initia1 volumetriccapacity of said motor in the engaged position of said clutch, a powerpressure intensifier for delivering operating power pressure to saidmotor, a manually operated master cylinder including a piston thereinfor controlling said power pressure intensifier and delivering adefinite proportional part of said operating pressure to said motor, astorage chamber, conduit means connecting said master cylinder with saidintensifier and said intensifier with said motor, means placing saidstorage chamber in Comunication with said conduit in response tomovement of said master cylinder piston to the off position thereofwhereby the decrease in volumetric capacity of said motor in the offposition of said fluid displaceable piston-like element thereof due towear in said plate is effective to deliver such excess of fluid to saidstorage chamber and thus automatically adjust for wear in said plate andmeans comprising a retractable stop effective to resist retraction ofsaid motive piston beyond a predetermined position thereof in the offdirection of movement of said clutch during periods between successiveclutch operations. whereby the volume displacement of said motive pistonwill remain substantially constant during successive operations of saidclutch for a given disengagement movement during the wear of saidfriction disc.

. 3. In an arrangement for transmitting operating pressure to a deviceto be moved through a predetermined range and automatically adjustingfor wear, said arrangement including means defining a linkage having anoff position which is gradually changed due to said wear, means defininga hydraulic pressure responsive motor including a piston-likedisplaceable element engaging said linkage for operating the samethrough said predetermined range in a manner such that as said weartakes place the volumetric capacity of said motor in the olf position ofsaid piston-like element is reduced by said piston-like element beingmoved by said linkage in additional increments in the volume reducingdirection beyond the initial off position thereof, said motor beinggiven an initial excess volumetric capacity in the off position of saidpiston-like element to allow for a predetermined amount of said wear andmeans for successively delivering hydraulic pressure to and relievingthe same from said motor, said means including a storage chamber, meansresponsive to the relieving of said delivery pressure effective todeliver said excess of hydraulic uld to said storage means as thevolumetric capacity of said motor is reduced by said wear, and controldening means effective to oppose the telescoping movement of said pistonbeyond the off position of said linkage eiective to prevent said pistonfrom being shaken beyond said off position which would cause undesirabletransfer of fluid to said reservoir in addition to the transfer of saidexcess fluid resulting from operations.

EDWARD A. ROCKWELL.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,934,206 Page Nov. 7, 19,332,060,692 Rockwell Nov. 10, 1936 2,135,617 Geyer Nov. 8, 1938 2,272,327Sauzedde Feb. 10, 1942 2,322,063 Schnell June 15, 1943 2,332,340 PriceOct. 19, 1943 2,334,383 Carr Nov. 16, 1943 FOREIGN PATENTS NumberCountry Date 547,465 Great Britain Aug. 28, 1942 662,766 France Mar. 25,1929

